1. Technical Field
The present invention relates to a voltage detection apparatus for a battery pack, and in particular, to a voltage detection apparatus which is applicable to a battery pack made of a plurality of serially connected cell groups each of which is a serial connection composed of a plurality of serially connected battery cells.
2. Related Art
This type of voltage detection apparatus is disclosed, for example, in a patent document JP-A-2011-253777. The voltage detection apparatus disclosed in this patent document performs voltage detection with respect to each of a plurality of cell groups that configure a battery pack. Specifically, this apparatus sequentially detects the voltage across the terminals of a respective plurality of battery cells configuring each of the cell groups. More specifically, this apparatus includes a pair of electric paths connected across the terminals of each of the battery cells, and an integrated circuit (hereinafter referred to as “monitoring circuit”) that has a function of detecting the voltage across the terminals of each of the battery cells via the pair of electric paths.
In the voltage detection apparatus mentioned above, the positive terminal of one of adjacent cell groups is connected to the negative terminal of the other of the adjacent cell groups via an electrically conductive member (e.g., wire). In such an apparatus, an application of an overvoltage across the pair of electric paths may impair the reliability of the monitoring circuit. In order to avoid this, the pair of electric paths are short-circuited by a bypass, or the pair of electric paths are connected to each other via a Zener diode.
In the configuration in which the pair of electric paths are short-circuited, when charge/discharge current is passed through the battery pack, an electromotive force is generated in the electrically conductive member due to its high impedance. Therefore, the charge/discharge current flows into the bypass that short-circuits the pair of electric paths adjacent to the electrically conductive member. As a result, the voltage in the pair of electric paths may drop due to the wiring impedance or the like. Thus, there is a concern that the accuracy of voltage detection for each of the battery cells is impaired. Further, in a configuration in which the pair of electric paths are connected to each other via a Zener diode as well, there is a concern that the accuracy of voltage detection for each of the battery cells is impaired when discharge current passes through the battery pack.